Various different systems are known for stacking objects. When stacking pieces of cloth or knitting, the fabric to be stacked is completely lacking in rigidity and is incapable of sliding over another piece of textile, thereby preventing newspaper or plastic bag stacking devices which rely on the physical characteristics of the object to be stacked from being used when stacking pieces of fabric. After cutting, garment manufacture requires various pieces of fabric (woven or knitted cloth) to be assembled in succession on assembly lines. These various different operations are performed at different locations along the assembly line and require numerous handling operations between one work station and the next. In addition, flat pieces of cut fabric are shaped so as to be suitable for covering a three-dimensional volume, and as a result their shape when laid out flat is generally highly irregular. They are incapable of sliding over one another and must be transported and put down from above on a stack which is being built.
In order to reduce handling time, and given that the various successive operations take different lengths of time, it is common to store part-finished articles temporarily at work stations in stacks for subsequent delivery to subsequent work stations, frequently via automated conveyor built systems.
Given the above-mentioned difficulties, the handling operations (stacking, turning, folding, etc . . . ) which are performed after a given manufacturing operation is completed to ensure that the partially completed work is properly presented to the next work station are currently performed manually. Although such stacking and possible folding operations are essential, they considerably increase manufacturing costs since work ceases at the associated work station while they are being performed.
Devices for stacking pieces of fabric have already been described in the following patent specifications: FR-A-No. 2 326 525, FR-No. 1-1 571 192, GB-A-No. 1 021 888, and U.S. Pat. No. 214 541. The devices described in these patent specifications are indeed capable of bringing together several pieces, but they are not capable of forming stacks each of which is of predetermined and adjustable shape as a stack, and each of which is capable of being built up from differently shaped articles.
U.S. Pat. No. 4 214 541 describes an arrangement in which article folding means are provided in a stacking apparatus, said folding means being synchronized with cutting operations in order to fold an article (a pillowcase) in half.
These means are constituted by a fixed folding bar in the form of a blade for forming the transverse fold line. The edges of the article fall under gravity on either side of the bar and the article is grasped from this position by grippers and placed on a conveyor belt. However, such a device is incapable of properly stacking irregularly shaped pieces.
A first object of the present invention is to provide an automatic stacking device enabling the operator of a sewing station, for example, to be released from the need to present articles properly to the next work station. The operator can thus concentrate solely on assembly work, per se.
A second object of the present invention is to provide a device which is entirely automated and which enables accurate and repetitive stacking to be performed in such a manner as to ensure that the stacks are presented in a constant manner and that they all include a given number of pieces.
A third object of the present invention is to provide a device capable of automatically unloading stacks, and thus constituting a step towards full automatiation, at least in the manufacture of certain simple items.